Method and apparatus for treating coarse materials



Feb. 4, 1941. 1 A. E. DOUGLASS METHOD AND APPARATUSFOR TREATING COQRSEMATERIALS Filed April 3, 1940 4 Sheets-Sheet 1 Ha. I

INVENTOR Y A/fred f Davy/ass ATTORNEY5' Feb. 4, 1 941. A. E. DOUGLASSAPPARATUS FOR TREATING COARSE MATERIALS METHOD AND Filed April 5, 1940 4Sheets-Sheet 3 cf) 9 u L INVENTOR ATTORNEY5 Feb. 4, 1941-. DQUGLASS2,230,833.

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Patented Feb. '4, 1941 UNITED STATES METHOD AND APPARATUS FOR TREATINGCOARSE MATERIALS Alfred E. Douglass, Catasauqua, Pa. Application April3, 1940, Serial No. 327,609.

9 Claims.

This invention relates to the treatment. of coarse crushed or granularmaterial in order to remove any moisture which might be retained thereinand to raise the temperature of the material to an elevated degree. Theinvention comprehends the process and apparatus for extracting valuableheat units from hot gases used for this p and thereby effects savings infuel. The invention may be used to advantage wherever coarse material isto be heated either by gases from a direct fired furnace or by wastegases carrying quantities of heat units from apparatus used inconjunction with the present invention for further treating thematerial. By way of exampleand not of limitation, the invention findsapplication in the treatment of limestone, phosphates, coal, ores, etc.

Various methods and apparatuses have been suggested in the prior art buthave proved to be unsatisfactory due primarily to the lack of propercontact of the gases with the individual particles making up thematerial to be treated. -A lack of uniformity of the bed through whichthe gases pass causes some portions of the material to be heated whileothers are left more or less unchanged. The bed will occasionally havethin places or a portion made up of segregated large size materialthrough which the gases readily pass so as to reach the grate memberbefore losing any substantial amount of heat which has a tendency toburn out the grate members unless expensive heat-resisting metals areused. In those apparatuses where the material travels over the grate bygravity, the time and amount of material treated are unpredictable andresult in a finished product of non-uniform character.

It is accordingly the purpose of this invention to raise the thermalefficiency of devices of this type and to deliver the finished productat a uniform'temperature or dryness.

The invention consists of a method and apparatus for removing anymoisture present in coarse material, raising the temperature thereof toa uniform elevated point and usually both. To this end, the material iscaused to form as a downwardly inclined bed of such slope or pitch thatth'ecombined effect of agitation and gravity results in completelyuniform resistance to air flow throughout thereby insuring uniformdistribution of the gases. The slope is. however, made insufficient tocause the particles to move by gravity without agitation; The materialto be treated is placed in a heating chamber having an entrance at oneend and discharge at the other end. The material is supported on adownwardly inclined gas permeable support comprising a. series ofoverlapping vertically spaced grates with stationary gratesalternatingwith moveable ones, the moveable grates are reciprocated continuously toadvance the material and constantly agitate the same while heated gasesare to flow through the material to either dry or elevate thetemperature or both. Due to the reciprocation of the moveable grates,the base of the bed is advanced which causes the bed to assume adefinite cross-section withthe smaller particles at the bottom and thelarger -ones at the top. This forming of a uniform cross-section resultsin several distinct advantages. The gases passing through the bedcontact substantially the same surface area of material at all pointsalong the bed so that when reaching the grate they have transferred-mostof the heat to the bed and have no ill effects 30 upon the supportingstructure. The grading of the bed from the large particles at the top tothe smallest at the bottom has the advantage of bringing the hottestgases in contact with those particles which need the most heat in orderto 25 penetrate to the core thereby to raise the temperature of theentire particle. It has been found in actual practice with one type ofmaterial when deliveringgases to the device at approximately 1500 F.that the exhaust gas temperature was about 300 F. and the material wasuniformly heated to about 1150 F.

The invention is particularly adapted for use in connection with thetreatment of material which is discharged into rotary kilns for furtherheat treatment such as in the burning of limestone. The heat developedin the rotary kiln is necessarily high for burning and the waste gasesissuing from the kiln carry large quantities of heat. The gas dischargeend of the kiln may be 40 directly connected with the present inventionand the heated waste gases utilized to furnish all or part of the heatrequired. When used in connection with a rotary kiln of this type, afurther advantage is noticed in that particles of partially treatedmaterial entrained in the gases are filtered out thereby increasing theefficiency of the process as a whole and obviating the use of separatorsin the conduits to the stack unless the material under treatmentcontains a substantial proportion of fines. Limestones treated by thepresent invention are found to. be uniformly heated and frequently haveundergone a partial calcination before entering the kiln which resultsin the use of a shorter kiln or when used with existing structures alonger efiective length of kiln for heat treatment. The apparatus of thepresent invention may be attached with little or no change to existingkilns or the housings for these kilns.

Other objects and advantages of this invention will appear from thefollowing detailed description taken in connection with the accompanyingdrawings, in which Fig. 1 is a sectional elevation of the device forpre-heating. 3

Fig. 2 is a vertical section of the device taken on line 2-2 of Fig. 1.

Fig. 3 is a side elevation, partly in section of a modified form of thedevice.

Fig. 4 is a fragmentary side elevation, partly in section of the upperportion of the grate mechanism.

Fig. 5 is a fragmentary plan elevation of a portion of the grateassembly.

Fig. 6 is a cross-sectional detail view of one of the supporting wheels.

Referring to the drawings and Figures 1 and 2 in particular, Idesignates an inclosed heating chamber having an inlet chute 2 connectedto a material hopper 3 through slide valve 4 at one end, and a fluidinlet port 5 at the other end. Material entering the chamber isdeposited upon a shelf 3 and after sufhcient material has 9.0-

cumulated upon the shelf to form a natural angle of repose, thedescending particles are distributed by the pile thus formed and pass onto an inclined grate assembly 1 to form a flat bed. The slope or pitchof the grate assembly should be less than that which will permit thelarger particles to roll downwardly freely. For the treatment of arelatively coarse material, such as crushed limestone of 1 /2 inch mesh,the pitch should preferablybe about 12. A steeper pitch may be used inthe treatment of finer materials, but appears to have no advantage. Thewalls of the heating chamber above the grate assembly are constructed ofceramic or other heat resisting material with the exception of the end.wall 8 adjacent the inlet chute which is protected by the incomingmaterial when the device is in operation. I

The grate assembly will now be described and it will be seen to comprisefixed grates 3 and moveable grates Hi, the fixed grates 9 are rigidlysecured to a stationary frame and all of the moveable grates I aresimilarly secured to a moving frame, forming separate unitarystructures. The stationery frame comprises inclined channel members IIand I2 supported by members l3 and I4 welded or otherwise secured toupright supports l5, l6, l1 and I8 in turn supported on lower horizontalplate members I3 and I-beams 20 and 2|. The fixed grates 3 are bolted'asat 22 to angular brackets 23,'welded or otherwise secured to framemember eachbracket extending forward beyond the fixed grates to deflectthe particles from the space between the side edges of the moving gratesl0 and the frame member The moving frame comprises inclined side members24 and 25 suitably braced by cross members 26, the side members carryinguprights 21 to which flanges, cast integrally at the side edges of themovable grates III, are secured as at 28. The members 24 and 25 are[secured to axles 29, supported by flanged wheels 3|], shown in detailin Fig. 6, provided with bronze bushings 3|, the wheels turning on theaxles and running on rails 82. the rails being bolted to angle members33 secured to and supported by uprights of the stationary frame by ahorizontal I-beam 34. Plates 35 and 3B cooperate with seals 31 to pre-,vent air from being drawn into the chamber below the grates.

The reciprocating motion of the moveable frame may be convenientlyaccomplished by two spaced eccentrics of the-conventional typecomprising eccentric rod 38 pivotally connected to axle 29. Movement ofthe axle 29 is transmitted to the moveable frame by strap 39 rigidlyconnected to this frame by housing 40 and channel 4| as shown in Fig. 4.The rods 38 pass through slots inthe rear wall 42 of the chamber andterminate in the usual strap 43 surrounding each eccentric disc 44. Acommon crankshaft is provided with a sprocket 45 driven through a chain46 by a variable speed motor, with speed reducer, indicated at 41. Itwill be seen .that grates l0 move in a horizontal plane between fixedgrates 3 and that the extent of the movement or throw depends upon theeccentricity of discs 44 on the crankshaft. In Fig. 4 the moving gratesare shown in their rearmost position and the maximum permissible advanceas being one-half their width, at which point the rear edge of eachmoving grate is covered by the leading edge of the fixed grate above it,thereby avoiding the passage of material treated between the grates. litwill also be understood that the'rate of travel of the bed andconsequently its thickness can be varied by changing the speed of themotor 41.

As shown in detail in Fig. 4, the fixed and moving grates areessentially similar and may be gray iron castings, the forward orleading edges of the fixed grates and the side edges of the movinggrates preferably being chilled in casting to resist wear of anyabrasive material which may be treated.

The adjacent grates are spaced a distance, usually it; inch,'to formhorizontal gas passageways, each grate also contains rows of taperedholes 48 near the forward edge and similar rows of tapered holes 49 nearthe rearward edge forming additional passageways for the heated gasesfrom the chamber Upon reciprocation of the movable grates it will beobvious from the construction shown that upon forward movement theopenings in the rear portion of the movable grate as well as the openingin the forward edge will be exposed to the material and the rearwardopenings of the stationary grate will be closed by the forward portionof the movable grate, the opposite condition taking place upon rearwardmovement of the movable grates. The space below the grate assemblyconstitutes an air tight exhaust chamber having side walls 50, bottom 5|and rear wall 42, as shown constructed of metal plate, but obviouslymight be made of other materials. The forward or discharge end of thechamber below the grates is closed by a refractory wall 52 upon whichthe lowermost fixed grate rests. Attached to the wall 52 is a trough 53into which the treated material is discharged, as shown in Fig. 1, thedischarged material then passes to the rotary kiln 54. Below the grateassembly 1 and positioned in the bottom 5| as shown in Fig. 2 is ascrevificonveyor 55 driven by a sprocket 58 and chain 51 from the motor41, this conveyor advancing any material which might leak through thegrates to the discharge trough 53. The heated exhaust gases from thekiln 54 are directed through the open- I ation of the device is not demotor 59 through belt having its intake connected through duct ii to thespace below the grates causes a reduction in the pressure in this spacesufllcient to cause the heated gases above the grate assembly toovercome the resistance presented by the grates and the thickness anddensity of the material bed to flow through the bed and into the duct6|, the gases passing vertically downwardly into the .tapered openingsin the grates and horizontally in a direction opposite to the travel orthe bed into the openings between the alternating grates. In this'mannerthe heated gases from the kiln obtain the maximum surface contact withthe particles making up the bed and consequently transfer most or theirheat to the material, the gases entering the duct 6| being at arelatively cool temperature.

The exhaust of the fan ill is connected through duct 62 to stack 63whereby the gases may issue to the atmosphere. The opening from thespace below the grate assembly is controlled by louvers havingadjustable controls 64 whereby the amount of heated gases passingthrough the bed and the speed thereof may be controlled.

When it be desired to pass any portion of the exhaust gases from thekiln over the material to heat the upper surface of the bed and thendirectlyto the stack 63 without going through the material bed, outletconnected to stack 63 by duct 66 is provided, the outlet 65 beingcontrolled by louvershaving adjustable controls 61 as clearly shown inFig.- 2.

By reference to Fig. 3 it will be seen that operndent, upon exhaustgases from a kiln, but may used with any type of heat generating devicesuch as furnace 68. The treated material when using this type of heatgeneratingmeans may discharge to chamber 89 from which it is removed asby a drag chain It, the remainder of the device being the same aspreviously described.

The operation of this device is extremely simple and because of thissimplicity is particularly adapted for use in its field. The materialentering the inlet chute forms a fiat bed upon'the grates of a desiredthickness which due to constant reciprocation of the moveable gratestravels uniformly to the discharge port. During this travel theparticles are constantly agitated, caused bytheir tumbling from onegrate to the/next. The linear'speed of these grates being very slowcause no vibration or noise and consequently very little wear takesplace on the moving parts. The heated gases are drawn through the bed inthe desired quantities, these gases traveling through .the Bed in twodirections to the vertical and hor-.

izontal openings in the grate assembly. The dispersion of the gasesthroughout the entire bed of material in this manner in connection withthe constant tumbling of the panticles results in the maximum surfacecontact or gas and material, the gases exhausted from the device havingthe major portion of the heat extracted. Due to the efllcient transferof the heat to the material the metal parts of the device need not beconstructed of expensive heat-resisting material.

From the foregoing, the embodiments of my invention will be fullyunderstood'but it is to be understood that the invention is notrestricted to the present disclosure to any extent otherwise thanrestricted by the manner in which such in vention is claimed.

Reference is hereby made to my copending applications Serial Nos.327,607 and 327,608, filed concurrently herewith.

I claim: 1. In a device for heat treating coarse or granu- 'lar.material which comprises an impervious chamber having a material inletat the upper end with the stationary grates alternating with the rmvablegrates, means to reciprocate the movable grates to advanceintermittently and constantly to agitate the material, means to supplyhot, gases to the upper compartment above the material, means to createareduced pressure in the lower compartment rtocause the hot gases to flowdownwardly through the material and support in that order, said suppo tbeing downwardly inclined at anangle less than the angle of repose ofthe material so that during advancement of the material along saidgrates it will be formed into and maintained in a bed of substantiallyuniform thicknms and the constant agitation thereof by saidreciprocating means will cause the material of the bed to be gradedaccording to particle size with the larger particles at the surface ofthe bed where they will be the first particles contacted :g'dthe hotgases passing downwardly through the and adjacent the uppermost grate toreceive thematerial from the material inlet and direct the same to thesupport in a uniform manner and thickness, means to reciprocate themovable grates to advance intermittently and constantly to agitate thematerial, means to supply hot gases to the upper compartment above thebed of-material, means to create a reduced pressure in the lowercompartment to cause the hot gases to how downwardly through thematerial bed and support in that order, said support being downwardlyinclined at an angle less than the angle of repose of the material sothat during advancement. of the material along said grates it will beformed into and maintained ina bed of substantially uniform thicknessand the constant agitation thereof by said reciprocating means willcause 'thematerial of the bed to be graded according to particle sizewith the larger particles at the surface of the bed where they particlescontacted by the downwardly through the bed.

3. In a device for heat treating coarse or granular material whichcomprises an impervious chamber having a material inlet at the upper endwill be the first hot gases passing permeable support for the materialto be treated dividing the chamber into upper and lower compartments.said support comprising a series of overlapping vertically spacedgrates, stationary- .65 and a material outlet at the lower end, a gasterial, means to create a reduced pressure in the lower compartment tocause the hot gases to flow downwardly through the material bed and.

support in that order, means connecting the upper compartment to areduced pressure area, and means controlling passage through said lastnamed means to vary the portion of gases delivered to the uppercompartment which passes through the bed, said support being downwardlyinclined at an angle less than the angled repose of the material so thatduring advancement of the material along said grates it will be formedinto and maintained in a bed of substantially uniform thickness and theconstant agitation thereof by said reciprocating means will cause thematerial of the bed to be graded according .to particle size with thelargerparticles at the surface of the bed where they will be the firstparticles contacted by the hot gases passing downwardly through the bed.

4. In a device for-heat treating coarse or granular material whichcomprises an impervious chamber having a material inlet at its upper endand a material outlet at its lower end, a wall upstanding from thebottom of the chamber extending laterally thereacross partially dividingthe same, an opening through the wall, a gas permeable support for thematerial to be treated dividing the chamber into upper and lowercompartments, said support comprising a series of overlapping verticallyspaced grates, stationary grates alternating with movable grates forsupporting a bed of material of substantial thickness, the lowermostgrate having an air-tight connection with the laterally extending wall,means to reciprocate the movable grates to advance intermittently andconstantly to agitate the bed, means to supply hot gases to the uppercompartment above the bed of material, means to createa reduced pressurein the lower compartment to cause the hot gases to flow downwardlythrough the material bed and support in that order, a conveyor in thebottom of the lower compartment extending through the opening in thelaterally extending wall to remove accumulated material passed throughthe support, and means to drive the conveyor, said support beingdownwardly inclined at an angle less than the angle of repose of thematerial so that dur-. ing advancement of the material along said gratesit will be formed into and maintained in a bed of substantially uniformthickness and the constant agitation thereof by said reciprocating meanswill cause the material of the bed to be graded according to particlesize with the larger particles at the surface of the bed where they willbe the first particles contacted by the hot gases passing downwardlythrough the bed.

5. The method of heat treating coarse or granular material whichcomprises continually forming a bed of material particles on a supportinclining downwardly at an angle less than the angle of repose of thematerial, applying mechanical pressureto the under portion of the bed toadvance the same at a substantially uniform rate under conditions ofcontinuous agitation to form a substantially uniform cross-section inthe bed with the larger particles at the top and the smaller particlesat the bottom, maintaining a source of heated gases above the bed, andmaintaining a reduced pressure below the bed to cause a portion of theheated gases to flow through the material the remaining gas flowingthereover.

6. The method of heat treating coarse or granular material whichcomprises forming and continuously maintaining a bed of material ofsubstantially uniform cross-section on a support inclined downwardly atan angle less than the angle of repose of the material, advancing saidbed of material downwardly over said support in a directionsubstantially parallel to the support, under conditions of continuousagitation to cause relative movement of the particles thereof and tograde the particles as to size, with the larger particles at the top ofthe bed, directing heated gases above the bed, maintaining a flow ofheated gases along the bed, maintaining a reduced.

at the top, supplying material to the upper end of the bed at the samerate as that at which it leaves the lower end of the bed, maintaining asource of heated gases above the bed, and maintaining a reduced pressurebelow the bed to cause the heated gases to flow uniformly through thebed and a multiplicity of vertically directed openings in the support.

8. The method of heat treating coarse or granular material whichcomprises forming and continuously maintaining a bed of material ofsubstantially uniform cross-section on a support inclined downwardly atan angle less than the angle of repose of the material, advancing saidbed of material downwardly over said support in a directionsubstantially parallel to the support, under conditions of continuousagitation to 'cause relative movement of the particles thereof and tograde the particles as to size, with the larger particles at the trip ofthe bed, directing heated gases above the bed, and maintaining a reducedpressure below the bed and causing the heated gases to flow uniformlythrough the bed in a multiplicity of vertically and horizontallydirected streams.

, 9. The method of heat treating coarse or granular material whichcomprises continuously forming a substantially flat bed of materialparticles of uniform thickness on a support inclining downwardly at anangle less than the angle of repose of the material, advancing the beddownwardly parallel along the support at a substantially uniform rateunder conditions of continuous agitation, maintaining a source of heatedgases above the bed and in contact therewith, and maintaining areduced'pressure below the bed to cause a portion only of the heatedgases to flow uniformly through the material.

ALFRED E. DOUGLASS.

